Potsdam Institute for Climate Impact Research (PIK) latest study shows
that if East Antarctica’s Wilkes Basin’s rim of ice lets go, it is likely to
trigger a persistent ice discharge into the ocean, resulting in unstoppable
sea-level rise for thousands of years to come. Using the ground profile under
the ice, the researchers used computer ice flow simulations under the ice
sheet.

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"East Antarctica's Wilkes Basin is like a bottle on a
slant," says lead-author Matthias Mengel, "once uncorked, it empties
out." The basin is the largest region of marine ice on rocky ground in
East Antarctica. Currently a rim of ice at the coast holds the ice behind in
place: like a cork holding back the content of a bottle. While the air over
Antarctica remains cold, warming oceans can cause ice loss on the coast. Ice
melting could make this relatively small cork disappear — once lost, this would
trigger a long term sea-level rise of 300-400 centimeters. "The full
sea-level rise would ultimately be up to 80 times bigger than the initial
melting of the ice cork," says co-author Anders Levermann.

"Until recently, only West Antarctica was considered unstable,
but now we know that its ten times bigger counterpart in the East might also be
at risk," says Levermann, who is head of PIK's research area Global
Adaptation Strategies and a lead-author of the sea-level change chapter of the
most recent scientific assessment report by the Intergovernmental Panel on Climate
Change, IPCC. This report, published in late September, projects Antarctica's
total sea level contribution to be up to 16 centimeters within this century.
"If half of that ice loss occurred in the ice-cork region, then the
discharge would begin. We have probably overestimated the stability of East
Antarctica so far," says Levermann.

Emitting greenhouse-gases could start uncontrollable ice-melt

Melting would make the grounding line retreat — this is where the ice
on the continent meets the sea and starts to float. The rocky ground beneath
the ice forms a huge inland sloping valley below sea-level. When the grounding
line retreats from its current position on a ridge into the valley, the rim of
the ice facing the ocean becomes higher than before. More ice is then pushed
into the sea, eventually breaking off and melting. And the warmer it gets, the
faster this happens.